This invention relates to a device for adjusting the angle of incidence of a rotor blade of a wind power installation.
In known devices, the rotor blade is rotatably mounted on a hub of the rotor of the wind power installation such that it can be adjusted in its angle of incidence—via a gearing provided in the area of its blade foot, said gearing being aligned essentially transversely to the longitudinal axis of the rotor blade—by means of a driving toothed wheel rotatably mounted on the hub and meshing with the gearing. However, the reverse arrangement is actually also known, namely that the hub can comprise the gearing and the driving toothed wheel being rotatably mounted on the rotor blade. In the same manner, there are arrangements with hydraulic rotary drives or cylinders whose linear movement is converted into a rotational movement by means of coupling bars.
The above mentioned open tooth-wheel drives for the adjustment of the angle of incidence of a rotor blade of a wind power installation are known, e.g. from DE 10140793. Here, the driving toothed wheel is driven by an electric motor and arrested, as a rule, by brakes located on the driving shaft. Due to the arresting of the driving toothed wheel, the rotor blade is also arrested in the desired angle of incidence.
As a rule, open tooth-wheel drives can be lubricated without any further problems since they utilize the entire available rotary area within the course of a given interval, and accordingly, all areas of the gearing can be regularly brought into contact with a lubricating device.
A suitable lubricating device is known from the article “Zentralschmieranlagen in Windkraftanlagen” (Central Lubrication Systems in Wind Power Installations)(T. Biesler, “Erneuerbare Energien” June 2002). Therein, a lubricating pinion consisting, for example, of felt or covered with felt meshes with a gearing of an open tooth-wheel drive. The lubricating pinion is mounted on a hollow-drilled axis which is provided on both sides with lubricant connections. The lubricant is passed via the axis to radial bores in the lubricating pinion and escapes again on its tooth flanks. Upon adjustment of the gearing by the driving toothed wheel, the lubricating pinion rotates synchronously with it and transfers lubricant to the areas of the gearing respectively being engaged with it.
Open tooth-wheel drives for adjusting the angle of incidence of a rotor blade of a wind power installation are distinguished from most of the other open tooth-wheel drives by being only in a defined operating position which is also designated as 0° position, during the predominant part of the operating period. The angle of incidence of the rotor blade corresponding to this position is applicable for the predominant part of all wind situations. The teeth of the driving toothed wheel and the gearing which are engaged with each other in the 0° position are subject to high loads which are caused, in particular, by the occurring torsional forces of the rotor blade. Other teeth of the driving toothed wheel and the gearing are loaded in rare cases (namely, when the rotor blade is moved—in strong wind conditions—from the 0° position into a different operating position for power reduction).
The primarily loaded areas of the driving toothed wheel and the gearing are subject to a high risk of corrosion since any possibly existing lubricant on loaded tooth flanks is displaced in the course of time so that the corresponding tooth flanks concerned will mesh with each other unlubricated after some time. Due to the high forces transferred, frictional corrosion can, thus, occur. The risk of corrosion is frequently yet reinforced by climatic effects (high humidity of the air, salt concentration of the air in coastal or offshore locations). Accordingly, these areas require a targeted, regular lubrication. At the same time, however, they cannot be reached or only barely by conventional lubricating methods since they are engaged with each other most of the time.
The above described lubricating pinions or most of the alternative lubricating devices are not suitable for tooth-wheel drives which predominantly remain in one operating position since a large part of the lubricant provided on all teeth of the pinion would drip off unused, would soil the hub and, thus, endanger the safety of the maintenance personnel accessing the hub. With conventional lubricating devices, a targeted lubrication of the primarily loaded areas of driving toothed wheel and gearing is not possible.
The primarily loaded areas of open tooth-wheel drives for the adjustment of the angle of incidence of a rotor blade of a wind power installation can only be specifically lubricated if the rotor blade is moved from its operating position into a lubricating position to make these areas accessible for conventional lubricating methods. This can be done, for example, during the natural non-working phases of the wind power installation (e.g. in the absence of wind). Although this procedure does not cause any operational production losses, it is problematic since a production phase can be very long and there is the risk that the load-bearing lubricating film does not survive this phase, and thus, damages to the gearing will occur. This problem presents itself especially at coastal or offshore locations where it is very rarely windless. Another possibility is the introduction of specified maintenance intervals during which the installation is shut down to move the rotor blades into a lubricating position. This procedure certainly ensures sufficient lubrication of the loaded areas, but will be connected with a production loss which especially the operating companies are unwilling to accept.